1. Field of the Invention
The present invention relates to a heart rate variability analyzing system, more particularly, to an electrocardiogram signal collecting apparatus for collecting electrocardiogram signals to be used in heart rate variability analysis. The electrocardiogram signal collecting apparatus in accordance with the present invention is of simple structure and low cost, and can be connected to a personal computer (PC) or a notebook computer.
2. Description of Related Art
The autonomic nervous system closely relates to human health. For example, autonomic ataxia may induce acute or chromic diseases such as cardiac disease, hypertension or even sudden death.
Heart rate variability analysis, which is a non-invasive examination method, has been recognized as a diagnostic indication of the autonomic nervous system. It is found that heart rate variability can be an indicator of the survival rate of a patient suffering severe disease. When a patient""s brain pressure increases, his/her heart rate variability will decrease. A brain-dead person""s heart rate variability disappears. According to the investigation of Framingham, if an old person""s heart rate variability decreases by one standard deviation, then the probability of death for this old person is 1.7 times of the probability for a normal person.
Heart rate variability includes a high-frequency (HF) component and a low-frequency (LF) component. The HF component is synchronous to the breath. The LF component is presumed to be relative to blood vessel movement or pressoreceptor reflex. The low-frequency component can be further divided into a very-low-frequency (VLF) component and LF component.
FIG. 1 is a schematic diagram showing a conventional heart rate variability analyzing system. With reference to FIG. 1, the conventional heart rate variability analyzing system comprises an electrocardiograph, a signal recorder, an analog to digital (A/D) converter and an appropriate analysis computer. In such a system, the measured heart rate needs to be manually corrected. In addition, spectrum analysis software is used in the appropriate analysis computer. The cost of the entire system is very high. Such a system has to be operated by a professional examiner. The operation of such a system comprises two steps: (1) on-line electrocardiogram (ECG) signal recording and (2) off-line analysis. The first step includes collecting ECG signals from a patient with an electrocardiograph and recording the signals on the signal recorder. The first step usually takes about 5 minutes to 24 hours. The second step includes converting the analog signals recorded in the signal recorder into digital signals by the analog to digital converter, transmitting the digital signals to the appropriate analysis computer to perform analysis by using the spectrum analysis software, and correcting the resultant heart rate through manual operation. The second step usually takes about 5 minutes to 2 hours. In practice, there is usually an interval of about 1 minute between these two steps. It is apparent that the conventional heart rate variability analyzing system has some disadvantages. Such a system is very expensive. The operation of the system takes a long period of time. This system occupies a large space. In addition, the system is so complicated that is necessary to be operated by a professional operator. Therefore, such a system is not possible to be used as a personal or home system.
One object of the present invention is to provide an electrocardiogram signal collecting apparatus, of which the structure is simple and cost is low.
Another object of the present invention is to provide an electrocardiogram signal collecting apparatus, which can be connected to a personal computer (PC) or a notebook computer to perform analysis.
A further object of the present invention is to provide an electrocardiogram signal collecting apparatus, which occupies a small space.
A further object of the present invention is to provide an electrocardiogram signal collecting apparatus, of which the operation takes a short period of time.
A further object of the present invention is to provide an electrocardiogram signal collecting apparatus, which can be operated easily.
In accordance with one aspect of the present invention, the electrocardiogram signal collecting apparatus comprises an electrode to sense heart constriction signals from the patient; a first stage filtering and amplifying section for receiving the signal from the electrode to filter out the DC component and the high frequency component and to amplify the remaining signal; a second stage filtering and amplifying section to further filter and amplify the signal from the first stage filtering and amplifying section; a photo-isolator having an input connected to the signal from the second stage filtering and amplifying section and an output, said output being electrically isolated from said input; an analog to digital converter receiving the photo-isolator output signal to convert said signal into a digital signal; and a printer input/output port connected between said analog to digital converter and a personal computer or notebook computer I/O port for receiving said digital signal from the analog to digital converter and transmitting the output signal to the personal computer or notebook computer.
In accordance with the present invention, the electrocardiogram signal collecting apparatus further comprises a battery to supply power to the first and second stage filtering and amplifying sections.
In accordance with a further aspect of the present invention, the electrocardiogram signal collection apparatus further comprises a battery monitor connected to the battery to monitor the battery power level and provide an alarm to the user when the battery power is low.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.